A mutant gene that suppresses the phenotypic expression of another usually mutant gene.

A device, such as a resistor or grid, that is used in an electrical or electronic system to reduce unwanted currents. ◇ A suppressor grid in a vacuum tube such as a pentode is designed to prevent the secondary emission of electrons from the plate. When electrons emitted by the tube's cathode strike the plate, their energies can be high enough to cause secondary emission of low-energy electrons from the plate, and these electrons can drift away into other positively charged electrodes in the tube (like the screen or the control grid), drawing current from the plate. A negatively charged suppressor grid near the plate repels these low-energy electrons and pushes them back toward the plate so that no current is lost, increasing the efficiency of the tube.